The number of gay and bisexual men contracting HIV has risen over the last 20 years because of an increase in numbers having unprotected sex, according to a new study.

Between 1990 and 2010, cases rose by 76 percent due to fewer people using condoms.

Researchers say this is due to the introduction of antiretroviral drugs (ART) that have been shown to be effective in treating the disease.

During this time there was a 26 per cent increase in the proportion having unprotected sex, according to the study by the Health Protection Agency (HPA) and University College London (UCL).

The latest data from the HPA shows that the number of people living with the HIV virus in the UK has almost reached 100,000.

The Guardian reports that HPA said one in 20 men who have sex with men in the UK now had HIV, with that figure rising to nearly one in 12 in London.

The study comes on the heels of a similar study that warned “unsafe sexual behavior” and a lack of testing by the individuals concerned as the reasons for the failure to cut the number of cases of HIV among gay and bisexual men in the last decade in England and Wales.

Sir Nick Partridge, chief executive of the Terence Higgins Trust said that advances in AIDS treatment had made HIV a less pressing issue in the gay community and had led to the false believe by some that it was less prevalent.

“One of the consequences of the advances in HIV treatment is that HIV is less visible than it was 25 years ago. To many gay men, it seems less prevalent than it was. The result is risks being taken and getting the risks wrong,” he said. “HIV is spread at the most intimate and passionate time and sometimes condoms are forgotten.”

However, Sir Partridge denied that gay men had become complacent.

“We know from our own research that the vast majority of gay men know that HIV is the most serious threat to their health and most gay men use condoms most of the time. If gay men had stopped using condoms, there would have been 80,000 more cases. This shows the importance of condom use. We need to increase condom usage and we need more regular testing.”

Dr. Valerie Delpech, who led the HIV surveillance at the HPA, adds: “Everyone should use a condom when having sex with new or casual partners, until all partners have had a sexual health screen.”

“Our research provides important evidence to support current UK public health recommendations on expanded HIV testing and higher levels of ART coverage, to reduce new infections among men who have sex with men.”

“However, we see it is also vital condom use education continues as not only does this have a strong limiting effect on the HIV epidemic, but only a modest increase in unprotected sex is enough to erode the benefits of other interventions.”

“We also encourage men who have sex with men to get an HIV and STI screen at least annually, and every three months if having condomless sex with new or casual partners – and clinicians to take every opportunity to recommend HIV testing to this group.

“Through combining earlier and more frequent HIV testing, programs that reduce unsafe sexual behavior and higher levels of antiretroviral coverage for those requiring it, we could substantially reduce HIV transmission in this group.”

The latest research, published in the PlOS ONE journal, also showed that the number of infections would have been 68 percent worse if antiretroviral drugs had not been introduced in the same period, and 400% greater if condom use by gay and bisexual men had stopped completely from 2000 onwards.

Last November, the HPA said that a record number of people in the UK were living with HIV, with the number of people with the virus reaching 96,000.

Alarmingly, health officials also warned that a quarter of people who have the human immunodeficiency virus are not aware they have been infected, the Daily Mail notes.

“We created a model reconstructing the HIV epidemic in men who have sex with men in the UK. In doing so, we were able to explore the interplay between HIV testing rates, antiretroviral treatment and sexual behavior on HIV transmission and incidence. By better understanding the driving forces behind the trends we’ve seen in the past, it will allow us to make informed choices to reduce new HIV infections in the future.”